1. Field of the Invention
The present invention relates to an image projection apparatus.
2. Description of the Related Art
Conventionally, an image projection apparatus (e.g., projector) for projecting an image onto a screen or the like is known (see, for example, Japanese Patent Application Laid-open No. 2012-163732). Some of image projection apparatuses generate an image based on image data transmitted from a personal computer, a digital camera, or the like and project the image. Some of the image projection apparatuses generate an image using a light modulation element (image generation element).
The light modulation element modulates light emitted from a light source based on an image signal to generate an image. To prevent uneven illuminance or the like, it is desirable that an illuminance distribution of the light projected to the light modulation element is uniform. Therefore, some of image projection apparatuses using the light modulation element are provided with a light tunnel between an image forming element and a light source. The light tunnel makes uniform the intensity of light to be projected.
The light tunnel is generally designed to match an aspect ratio of a projection image. In other words, when the aspect ratio of the projection image is 4:3, the light tunnel is also designed so that its cross-sectional shape is a rectangle whose aspect ratio is 4:3.
However, the design of the light tunnel is based on an assumption that a relative position between the light tunnel and the light modulation element is unchanged, and therefore it is not suitable for a case in which the relative position changes. In other words, if the relative position between the light tunnel and the light modulation element changes, part of the light modulation element deviates from an area illuminated with the light having passed through the light tunnel. In this case, because the part of the light modulation element that deviates from the illumination area cannot take part in image generation, a problem, such as so-called vignetting, occurs.
In view of the above-described conventional problems, there is a need to provide an image projection apparatus capable of using the entire surface of an light modulation element that fits in an illumination area without any trouble even if a relative position between the light modulation element and a light tunnel changes due to, for example, rotation of the light modulation element by a predetermined angle.